Combination ring and central drill bit drilling equipment



Jan. 4, 1966 G. LAGERSTROM COMBINATION RING AND CENTRAL DRILL BIT DRILLING EQUIPMENT Filed Feb. 21, 1961 4 Sheets-Shae IN V EN TOR.

" V/IHI Jan. 4, 1966 G. LAGERSTRQM COMBINATION RING AND CENTRAL DRILL BIT DRILLING EQUIPMENT Filed Feb. 21. 1961 4 Sheets-Sheet 5 Jan. 4, 1966 a. LAGERsTROM COMBINATION RING AND CENTRAL DRILL BIT DRILLING EQUIPMENT 4 Sheets-Sheet 4 Filed Feb. 21, 1961 I I ii INVENTOR.

3,227,230 COMBINATION RING AND CENTRAL DRILL B DRILLING EQUIPMENT Gunnar Lagerstriim, Naclra, Sweden, assignor to Atlas Copco Alrtiebolag, Nacka, Sweden, a corporation of Sweden Filed Feb. 21, 1961, Ser. No. 90,348 19 Claims. (Cl. 175-214) This invention-relates to means and method for drilling in hard soil containing boulders and more or less solid rock and/or in rock covered by a soil cap of varying composition and to a method of drilling in such materials. Such diilling is often desired in connection with investigation drilling for hydro electric power plant dams, for power plants, in harbour construction, for geological investigations, for cement injection' and ground stabilization, for investigation of oil deposits, piling and other work for building construction and for various other purposes. Such drilling is usually rather expensive and one object of the present invention is to provide means for reducing the costs for such drilling. A further object of the invention is to enable such drilling to be carried out by means of substantially conventional hammer drills.

depths. Another object is to provide equipment which substantially consists of conventional elements.

A still further object of the invention is to enable such drilling to be carried down to considerable For the above and other purposes I provide a drilling equipment comprising a ring drill bit, a central drill bit and rod assembly arranged to operate axially through said ring drill bit, means for transmitting rotational movement from said assembly to said ring drill bit, and tube means enclosing said assembly and arranged to permit retraction of the assembly through said tube means to permit relative rotation of the ring drill bit with regard to the tube means. In operation the invention consists in the method which comprises advancing a tube ortrain of tubes and a ring drill bit operating in front of said tube or train of tubes through the ground together with a drill rod or train of rods and a central dr'dl bit,rotating said central drill bit and said ring drill bit by said rod without rotating said tube or tubes, and retracting said central drill bit through said ring drill bit and tube or tubes. A preferred embodiment of the invention comprises a percussive ring drill bit with radially arranged hard metal cutting inserts, a percussive'central drill bit with hard metal cutting insertsand arranged to pass axially through said ring drill bit, a bit adapter having shoulders for transmitting axial blows to said central drill bit and said ring drill bit, respectively, biog/receiving surfaces on said central drill bit and said ring drill bit arranged for engaging said shoulders to receive blows and disposed adjacent said hard metal inserts, a first means for coupling the central drill bit to said bit adapter arranged to enable the bit adapter to rotate the central drill bit and to retract the central drill bit from a hole, a secthrough said train of drill tubes, and coupling means between the ring drill bit and the extreme tube arranged to entrain the ring drill bit in axial motion of said extreme tube with a lost motion in both axial directions but permitting the ring drill bit to be rotated relative to the extreme tube by the bit adapter, a main adapter at the a ameter end shoulder 58 forming a thrust bearing for the 3,227,230 Patented Jan. 4, 1966 "ice opposite end of said trains arranged for transmitting axial blows to both trains but for transmitting rotation to the central train only, and means for supplying flushing medium to said bits.

In the accompanying drawings two embodiments of drilling equipment for carrying out the invention are illustrated by way of example. It should, however, be understood that the invention may be modified in several difierent ways within the scope of the appended claims.

FIG. 1 is a side view and partial axial section of a main adapter and pertaining drill rod and tube of an equipment according to the invention.

FIG. 2 is a side view of a drill tube coupling.

. FIG. 3 is a side view and partial longitudinal section showing the bits, the bit adapter and adjacent drill tube and rod of the equipment shown in FIG. 1.

FIG. 4 is a cross section on line IV-IV in FIG. 3.

FIG. 5 is a side view and partial longitudinal section of the main adapter and the co-operating portions of drill rods and tubes of a second embodiment of the invention.

FIG. 6 is a side view and partial longitudinal section showing the bit adapter and bits, as well as the drill rod and tube utilized in the second embodiment of the invention shown in FIG. 5.

FIG; 7 is a cross section on the line VIIVII in FIG. 6.

FIG. 8 illustrates a drill tube coupling for the embodiment ofFIGS. 5-7.

FlG. 9a illustrates on a reduced scale a drill rig for the drilling equipment of FIGS. l-S.

FIG. 9b is a continuation of the lower end of FIG. 9a and shows the manner in which the drill bits penetrate soil and rock.

The drilling equipment illustrated in FIGS. 1-4 consists of a main adapter 1, which is provided in conventional mannerwith a Leyner type shank 2 adapted to fit the chuck of a hammer drill 3, FIG. 9a, provided with a suitable rotation mechanism 4 for rotating the adapter 1 and with a hammer piston 5 for delivering blows to the shank 2 of the adapter. The drill may be provided with other drill steel rotation means if desired. The drill may be provided with conventional flushing means for'providing flushing medium to a passage 6 in the adapter 1. The adapter 1 forms a socket 7 which is internally screw threaded to receive a corresponding screw threaded end 8 of a drill rod 9 having a flushing medium passage 10 communicating with the passage 6 and an upper end surface ll engaging a corresponding bottom shoulder 12 in the socket 7 for transmission of percussion energy delivered by the drill 3 through the main adapter to the rod 9. A flushing water bushing 13 is provided around the drill rod 9 at the lower end of the socket 7 and has a flushing water connection 14 through which flushing water from a suitable source may be supplied to a bore 15 in the bushing around the drill rod 9. The adapter 1 has a large diupper end surface 59 of the bushing 13 which permits the adapter to rotate relative to the bushing 13. Said thrust bearing also serves to transmit blow energy from the adapter to the bushing. A drill tube 16 is arranged below the bushing 13 around the drill rod 9 and has an upper end surface 17 which is engaged by a lower end surface 18 of the bushing 13 for transmitting blows from the adapter 1 through the bushing 13 to the tube 16. The tube 16 has welded thereon a sleeve 19 which extends upwards around the bushing 13 as obvious from FIG. 1. An ()-ring 20 forms a seal between the bushing 13 and the sleeve 19 and a second O-ring 21 forms a seal between the bushing 13 and the rod 9, so that escape of flushing Water at these points is prevented. A retainer clamp 2 2 is provided with a forked portion 23 and an annular portion 3 24 which engage the drill tube 16 below the sleeve 19 and the main adapter 1 above the socket 7 so that drill tube 16 may be lifted by means of the drill when the adapter 1 is raised.

The drill tube 16 and sleeve 19 is the upper element of a train of drill tubes 16, 25, 26 which enclose a train of drill rods 9, 27 and which are not rotated during penetration in the soil and which are coupled together by means of couplings 28, FIG. 2, which couplings comprise sleeves 28 identical with sleeve 19 and welded to the drill tubes 25. Said sleeves may have bayonet type internal recesses 29 engaged by lugs 30 provided on the co-operating end of the drill tube 16, as best obvious from FIG. 2. The recess 29 has a portion 31 engaged by the lug 30 when the drill tubes are pushed together and a portion 32 engaged by the lug 30 when the tubes are pulled apart and both preventing uncoupling of the tubes by rotation of the train of drill tubes. The tubes 16 fit in the sleeves 28 with ample clearance so that assembly is easy and so that a passage for the escape of flushing water from within the tubes to the outside of the tubes is provided at least when the tubes are pulled somewhat apart. The flushing water escaping at the tube couplings serves to lubricate the outside of the train of tubes.

The drill rod 27 is coupled to a bit adapter 33 by means of a screw threaded sleeve 34 which fits corresponding rounded screw threads 35 and 36 on the drill rod 27 and the upper end portion of the bit adapter 33, respectively. The flushing medium passage 10 extends through the rod 27 and the bit adapter 33 and percussion energy is transmitted from the drill rod 27 through the end surface 37 to the end surface 33 of the bit adapter. The bit adapter 33 is provided with a screw threaded lower end portion 39 on which is screw threaded the socket portion 40 of a central drill bit 41 provided with hard metal inserts 42 forming radial cutting edges 43 on the bit. Percussion energy is transmitted from the bit adapter 33 by a surface 44 engaging a shoulder 45 adjacent the inserts 42 in the lower end of the bit 41. The bit adapter 33 is provided with heavy external splines 46 which engage corresponding grooves 47 within a sleeve portion 48 of a ring drill bit 49, said bit having radially arranged hard metal inserts 50 forming radial cutting edges 51. The grooves 47 in the sleeve portion 48 ends with shoulders 52 adjacent the hard metal inserts 50 in the ring drill bit and adapted to be engaged by corresponding end surfaces 53 on the splines 46 for transmitting percussion energy from the bit adapter 33 to the ring drill bit 49. The sleeve portion 48 is provided at the upper end with a flange 54 which is movable between the lower end surface 55 of the tube 26 and a pair of locking members 56 secured at the lower inner end of a sleeve 57 screw threaded or otherwise secured to the tube 26. It is obvious that by this arrangement a certain lost motion in axial direction is provided between the ring drill bit 49 and the tube 26 and the tube 26 cannot rotate the ring drill bit 49 but is capable of retracting the ring drill bit when the tube is withdrawn from a hole in the earth or in rock.

In the embodiment of the invention illustrated in FIGS. 5-8 all parts which are equivalent to the parts of the equipment already described are indicated by the same reference numerals as used in connection with the equipment above described. The difference consists substantially in this that the drill tube section 71, 72 and the sleeve 73 in the embodiment of FIGS. 5-8 are coupled together by means of internal coupling sleeves 74, 75 which are provided with rounded screw threads and screw threaded into the tube sections 71-73 as indicated at 76. In this manner a completely smooth external surface of the train of drill tubes is obtained so that feeding of the drill tubes into the ground as Well as retraction of the drill tubes from the ground when the hole has been completed requires less power and the risk that the train of drill tubes would stick in the hole is substantially reduced or eliminated. At the upper end of the drill tube 71 a bushing 77 is screw threaded into the drill tube at 78 and said bushing is provided with an external flange 79 which rests on the upper end surface 80 of the tube 71 and furthermore the flushing water supply bushing 13 has in this case an external flange 81 which is carried by the flange 79 and which serves to transmit percussion energy from the main adapter 1 over a shoulder and bearing surface 82 on the main adapter through the flange 79 to the tube 71. The main adapter 1 is in this case provided with a flushing water bushing 83 through which flushing water may be supplied to the flushing water passage 6 in the main adapter and the passage 10 in the drill rods 9, 27. A split retaining ring or clamp 84 having two projecting wings is provided around the upper end of the tube 71 and held in position by chain members 85 fixed to the drill or the drill slide 94 and coupled to the wings of the ring 84 over draw bars 86 and springs 87. This arrangement makes possible retraction of the train of tubes 71.-73 under vibration transmitted from the idle running drill which is often helpful during the pulling out operation of the train of tubes. The bushing 77 forms a cylindrical seal with the bushing 13 and the latter is axially movable relative to the bushing '77 during operation and as a result of the operation of the drill percussion energy may therefore be transmitted to the flushing water column in the space 99 between the train of drill rods 9, 27 and the train of tubes 71-73 thereby producin a very eflicient flushing of the clearance passages between the ring drill bit 49 and the bit adapter 33 as well as between the ring drill bit 49 and the sleeve 73 and in order to obtain this effect a check valve 88 is provided in the flushing water supply 14 to the bushing 13. A pressure gauge 89 may be provided before or after the check valve 88, and by observation of the indications thereon and particularly of an undue pressure rise the operator may follow the operation of the bits and the conditions prevailing at the bits. A rise of pressure indicates clogging of the bits which may give the operator an indication to change the feed pressure or to take other suitable steps. For instance, if the operator finds that the passages around the bits have been clogged he may work the feeding motor forward and reverse thereby causing a pumping of flushing Water through said passages by reciprocation of bushing 13 in the bushing 77. This is by reason of the fact that the passages are kept filled with water through supply fitting 14 and consequently, bushing 13 will act as a plunger or ram to force the water through the passages.

Passages 95, 96 may be provided in the sleeves 74 and tubes 71, 72 for water serving to lubricate the outside of the train of tubes.

In operator the equipment accordingto FIGS. 5-8 functions in substantially the same way as indicated in connection with the equipment illustrated in FIGS. 1-4.

In FIGS. 9a and b the drilling equipment of FIGS. 5-8 is illustrated in combination with a conventional wagon drill comprising a movable base 60 carrying a feed bar 61 for a rock drill 3 and a suitable motor 62 capable of moving the drill 3 up and down the feed bar by means of chains 63 it being understood however, that any other conventional mounting and feeding apparatus for the hammer drill capable of moving the hammer drill up and down or forward and backward on a suitable feed bar may be used said mounting forming no part of the invention.

In operation for drilling a hole in the soil 64 and boulders 65 or rock 69 covered by said soil a leading tube 72 with a sleeve 73 and a ring drill bit 49 is placed and held in suitable guides 66, 66 at the leading end of the feed bar 61. Before the leading tube is raised from the ground into the guides 66 a bit adapter 33 with a central bit 41 secured thereto is coupled to a drill rod 27 by a coupling sleeve 34 and moved into the tube 72 until the bit adapter 33 enters the grooves of the ring drill bit 49. A flushing water bushing 13 and bushing 77 is then fitted in the upper end of the tube 72. The length of the bit adapter and tubes and rods is such that the threaded end of rod 9 projects above the bushing 13 andthe main adapter 1 which is fitted in the drill may now be fitted to the rod 9. After connection of flushing water hoses to the flushing water bushings 13, 83 the drilling operation may be started. i t

The hammer drill? is then started as Wellas the feeding motor 62 and the central bit as well as the .ring drill bit are advanced through the soil. Flushing water is supplied through the central passage as well as through the space 90 between the drill rod and the tube 72 so that mud and debris are prevented from entering the clearance 68 between the bit adapter and the ring drill bit 49 as well as between the ring drill bit andthe sleeve .73. The central drill bit as well as the ring drill bit are rotated during the operation of the hammer drill preferably by the separate drill rotation motor 4 but it is understood that hammer drills may also be used in which rotation is obtained in conventional manner from a rotation mechanism actuated by the hammer piston 5 of the drill 3. The drill tube 72. 73 is advanced through the hole 91 produced by the ring drill bit 49 by the feedingaction of the drill combined with impacts transmitted to the drill tube 72 from the adapter 1 through the bushing 13 and the flange 79 and the upper surface 80 of the drill tube. Rotation is not imparted to the drill tube since the main adapter forms a bearing with the bushing 13 at58, 59 01*82 and .by this arrangement ithas been found that the equipment according to the invention may penetrate through soil and rock of very considerable depth without the necessity of the provision of extremely powerful drill rotation mechanisms, since the resistance to rotation of the central drill bit as well as the ring drill bit does not increase materially with the depth of the hole,

When one length of drill rodand tube has been forced into the ground the main adapter 1 is uncoupled from the drill rod. The bushing 13 and bushing 7.7 are then removed and the drill is retracted a suflicient distance that a further length oftube 71 with bushing 77 .and bushing 13 and with rod 9 and coupling 34 may be fitted.

By means of the winch 70 and the means 84457 the tube 71 is raised over the tube 72 and rod already forced into the ground while the rod and coupling in the raised tube is held by hand. The rod 9 with the coupling 34 is then coupled to the rod already in the ground. The drill is thereafter lowered so that the tube 71 may be coupled together with the bit adapter 33 and the centraldrill bit All may be retracted leaving the ringdrill bit and the train of tubes in the ground. If it is now desiredtodrill further into the solid rock 69 as at 93 the bit adapter 33 and the central drill bit 41 is removed from the train of drill rods and the central drill bit without the bit adapter is fitted to the lower end of the drill rod 27 whereafter the train of drill rods may again be lowered into the hole. Theflushing water bushing 13 may now be removed or brought out of operation and further drill rods added to the train of drill rods so that penetration can continue in the solid rock and a hole 93 can be drilled to the desired depth.

If it is desired to blast the rock 69 without removing the soil cap a plastic tube may be provided in the hole after removal of the train of drill rods; Such tube may be of such dimension that it can enter through the ring drill bit into the hole 93 and afterwards the. ring drill bit H may be withdrawn together with the train of tubes 71- 73 by retraction of the drill or by meansof the separate iconnected to the members 85 or the clamp 22 in case of equipment of FIGS. -14.

For other purposes the clean hole provided by the train of tubes 71-73 or 16, 26 after removal of the central rod and bit assembly may be used for investigation or for casting a pile or for other purposes as the case may be. In connection with pile casting the train of tubes and ring drill bit may be made of .cheap material so that they can be left in the hole together with the concrete forming the body of the pile.

The equipment of FIGS. 1-4 is handled in substantially the same way as above described as would be obvious to anyone skilled in the art.

The drilling equipment above described should only be considered as an example and may be modified in several drill bit with radially arranged hard metal cutting inserts,

a percussive central drill bit with hard metal cutting inserts and arranged to pass axially through said ring drill bit, a bit adapter "having shoulders for transmitting axial blows to said central drill bit and 'said ring drill bit, respectively, blow receiving surfaces on said central drill bit and said ring drill bit arranged for engaging said shoulders to receive blows and disposed adjacent said hard metal inserts, a first means for coupling the central drill bit to said bit adapter arranged to enable the bit adapter to rotate the centraldrill bit and to retract the central drill bit from a hole, a second coupling means for coupling the ringdrill bit to the bit adapter arranged toenable the bit adapter to rotate the ring drill bit and to be retracted from the ring drill bit without removing thering drill bit from a hole, a train of coupled drill rods coupled to the bit adapter, a train of coupled tubes enclosing said train of drill rods and providing a passage for removing said train of drill rods and the bit adapter and the centraldrill bit axially through said .train of drill tubes, and coupling means between the ring drill bit and the extremelower tube of said train of tubes arranged to provide a lost motion in both axial directions between said lowerltube and said ring drill bit but permitting the ring drill bit to be rotated relative to said lower tube by the bit adapter, a main adapter at the opposite ,end of said trains arranged for transmitting axial blows to both trains but tor transmitting rotation to the central train only, and means for supplying flushing medium to said bits.

2. A drilling equipment according to claim 1, in which a passage is provided between said train of 'drill rods and said train of drill tubes for conveying flushing medium to the ring drill bit, and means for supplying flushing medium to said passage.

3. A drilling equipment comprising a ring drill bit, a central drill bit and rod assembly arranged to operate axially through said ring drill bit, a main adapter connected to said assembly and arrangedtotransmit percussion energy and rotation energy to said central drill bit and rod assembly, means for transmitting rotational movement from said assembly/to said ring drill bit, tube means enclosing said assembly and arranged to permit retraction of the assembly through saidtube means, coupling means between said tube means and said ring drill bit arranged to permit relative rotation of the ring'drill bit with regard to the tube means and retraction of the ring drill-bit by the percussion energy from the adapter to the bushing, and

an end face on the bushing and a cooperating end face on saidtube means for transmitting percussion energy from,

the flushing water bushing to the tube means.

4. A drilling equipment according to claim 3 in which a check valve is provided in the flushing water supply means of the bushing, and in which an axial lost motion is provided in said coupling means between the tubemeans and the ring drill bit.

5. A drilling equipment according to claim 4 associated with a percussion drill and provided with a clamp for engaging the tube means for pulling said tube means out of a hole, and resilient means connecting said clamp to said percussion drill.

6. A drilling equipment comprising a ring drill bit, a central drill bit and rod assembly arranged to operate axially through said ring drill bit, means for transmitting rotational movement from said assembly to said ring drill bit, tube means enclosing said assembly and arranged to permit retraction of the assembly through said tube means, coupling means between said tube means and said ring drill bit arranged to permit relative rotation of the ring drill bit with regard to the tube means and retraction of the ring drill bit by the tube means, a main adapter arranged to fit said central drill bit and rod assembly and to transmit percussion and rotational energy to said assembly, a flushing water passage between said assembly and said tube means, a flushing water supply bushing fitted on the assembly and provided with passages for leading flushing water to said passage between said assembly and said tube means, a shoulder on said main adapter arranged for transmitting percussion energy through said bushing to said tube means but permitting rotational movement of the adapter relative to said tube means, and a clamp for holding said tube means and said main adapter together axially.

7. In rock drilling apparatus adapted for drilling coaxial bores of two different diameters with both axial percussive motion and rotary motion, the combination which comprises a percussive ring drill bit having cutting edges disposed therearound defining the diameter of the larger of said bores and an open central passage axially disposed through said ring drill bit, a central percussive drill bit having cutting edges disposed therearound defining the diameter of the smaller of said bores, the diameter of said central drill bit being less than the internal diameter of said axial passage in said ring drill bit for free axial movement and retraction of said central drill bit through said passage, a bit adaptor connected to said central drill bit and coaxially disposed with respect thereto in said passage, means on said bit adapter for transmitting axial drilling percussions to said central drill bit, cooperating and engaging substantially transverse surfaces on said bit adaptor and said ring drill bit for transmitting axial drilling percussions to said ring drill bit only in a drilling direction, said bit adaptor being freely axially retractable from said ring drill bit in the opposite direction, and engaging means on said bit adaptor and said ring drill bit for transmitting rotary motion from said bit adaptor to said ring drill bit and being freely axially disengageable upon retraction of said bit adaptor from said ring drill bit.

8. Apparatus as recited in claim 7 in which said means for transmitting said rotary motion from said bit adaptor to said ring drill bit comprise cooperating and engaging axially disposed splines on said bit adaptor and in said passage through said ring drill bit, the smallest internal diameter defined by the inner edges of said splines in said ring drill bit being greater than the diameter of said central drill bit, and said splines on said adaptor and said ring drill bit being freely axially disengageable upon retraction of said bit adaptor in the direction opposite to the direction of drilling.

9. Apparatus as recited in claim 8 in which the ends of said splines on said bit adaptor adjacent said central drill bit connected thereto form said surfaces for transmitting said axial percussions from said bit adaptor to said ring drill bit, and in which substantial clearance is maintained between said engaging splines for flow of flushing water therebetween.

10. Apparatus as recited in claim 7 which also includes non-rotating hollow tube means of slightly less outside diameter than said larger diameter defined by said cutting edges on said ring drill bit and disposed coaxially around both said bit adaptor and said ring drill bit, said ring drill bit being freely rotatable within said tube means, coupling means on said tube means and said ring drill bit for axial coupling thereof and notwithstanding rotation of said ring drill bit within said tube means, the internal diameter of said tube means being greater than the greatest diameter of said bit adaptor and said central drill bit for free axial retraction thereof through said tube means.

11. Apparatus as recited in claim 19 in which said tube means comprises a train of individual tube segments and coupling sleeves connecting said individual tube segments into said train, said coupling sleeves being hollow with an inside diameter greater than the greatest diameter of said bit adaptor and central drill bit for axial retraction thereof through said sleeves.

12. Apparatus as recited in claim 11 which also includes means for introducing flushing water into said train of tubes and passages at said coupling sleeves for flow of said flushing water from the inside to the outside of said train of tubes.

13. A drilling equipment according to claim 12, in which each coupling sleeve comprises a bayonet type sleeve, lugs on the cooperating end portions of the tubes, and recesses in each sleeve for accommodating said lugs for preventing uncoupling of the joint by turning when the joint is exposed to a pulling or pushing force, respectively.

14. A drilling equipment according to claim 12 in which each coupling sleeve has a screw threaded portion with rounded screw threads, a mating rounded screw thread on the cooperating end portions of the tubes, said screw threads on the sleeves and tubes forming clearance spaces therebetween to permit flushing water to escape from the inside to the outside of the tubes.

15. Apparatus as recited in claim 10 in which said coupling means between said tube means and said ring drill bit includes an axial lost motion therebetween and comprises axially slidable engaging means on said tube means and said ring drill bit for interlocking engagement upon axial movement of said ring drill bit in drilling direction and of said tube means in the opposite direction.

16. Apparatus as recited in claim 19 which also includes central rod means connected to said bit adaptor and within said tube means for transmission of said axial drilling percussions and said rotary motion thereto, and a main adaptor engaging the ends of both said rod means and said tube means opposite to said drill bits and including means for transmitting said axial drilling percussions to said central rod means and said tube means and for transmitting said rotary motion to said central rod means.

17. A drilling equipment according to claim 16, in which a flushing water passage is provided axially through said central drill bit and rod assembly and between said assembly and said tube means a flushing Water passage in said main adapter communicating with the passage in the assembly and in which a flushing water bushing is fitted swivelly on said main adapter and communicates with said passage in the adapter for leading flushing water to the passage in the assembly, and in which a second flushing water bushing is fitted on the assembly for supplying flushing water to the passage between the assembly and the tube means.

18. In rock drilling apparatus adapted for drilling coaxial bores of two different diameters with both axial percussive motion and rotary motion and which embodies a large diameter hollow rotatable ring drill bit and a smaller diameter coaxial central drill bit and non-rotating outer tube for carrying and surrounding both said drill bits and an inner drive rod for imparting both said axial percussive and rotary motions, the combination which cornprises a bit adaptor for direct engagement with and between said drive rod 'andsaid central drill bit and disposed coaxia lly within said ring drill bit, means on said bit adaptor for transmitting from said drive rod to said central drill bit both said axial percussive and rotary motions and including threaded portions at each opposite end of said bit adaptor for engaging respectively said drive rod and said central drill bit, means on said bit adaptor for transmitting both said axial percussive and rotary motions from said drive rod to said ring drill bit independently of said non-rotating tube and including axially extending splines on said bit adaptor for driving engagement with saidring drill bit for imparting said rotary motion thereto and substantially transversely disposed abutment surfaces on said bit adaptor for engagement with cooperating surfaces on said ring drill bit for transmission of said axial percussive motion thereto, said splines on said bit adaptor being freely axially disengageable with said ring drill bit and the greatest outside diameter of said bit adaptor and said central drill bit being less than the internal diameter of said hollow ring drill bit for free axial retraction of said bit adaptor and said central drill bit through said hollow ring drill bit in a direction opposite to the direction of drilling.

19. In rock drilling apparatus adapted for drilling coaxial bores of two diiferent diameters with both axial percussive motion and rotary motion and which embodies a large diameter hollow rotatable ring drill bit and a smaller diameter coaxial central drill bit and non-rotating outer tube for carrying and surrounding both said drill bits and a central drive rod for imparting both said axial percussive and rotary motions, the combination which comprises a main adaptor for disposition at the end of said non-rotating tube means and said central drive rod means opposite to said drill bits, means at the upper end of said main adaptor for driving engagement with drill motor means for imparting said axial percussive and rotary motions, means in said m-ain adaptor for driving engagement with said central drive rod for imparting thereto both said axial percussive and rotary motions, an annular shoulder at the lower end of said main adaptor and of substantially larger diameter than said central drive rod for engaging and transmitting axial percussive motion to said tube means, and means adjacent said annular shoulder for engaging the upper end of said tube means for free rotation of said main adaptor with respect to said tube means and for axial retention of said tube means upon substantial axial movement of said main adaptor.

References Cited by the Examiner UNITED STATES PATENTS 484,764 10/1892 Elder 285-13 X 1,391,626 9/1921 Gilthorpe 257 X 1,943,103 1/1934 Benson 175-62 X 1,997,731 4/1935 Humason 285-376 X 2,292,867 8/1942 Charles 175138 X 2,323,027 6/1943 Gerstenkorn 175-321 2,675,213 4/1954 P0016 (it al 175 257 X 2,698,761 1/1955 Claypool et al. 285-376 X 2,699,182 1/1955 Baldridge 285-397 X 2,884,227 4/1959 Hjalsten 175-405 X FOREIGN PATENTS 514,524 10/1952 Belgium.

819,901 10/1937 France.

CHARLES E. OCONNELL, Primary Examiner.

BENJAMIN HERSH, Examiner. 

6. A DRILLING EQUIPMENT COMPRISING A RING DRILL BIT, A CENTRAL DRILL BIT AND ROD ASSEMBLY ARRANGED TO OPERATE AXIALLY THROUGH SAID RING DRILL BIT, MEANS FOR TRANSMITTING ROTATIONAL MOVEMENT FROM SAID ASSEMBLY TO SAID RING DRILL BIT, TUBE MEANS ENCLOSING SAID ASSEMBLY AND ARRANGED TO PERMIT RETRACTION OF THE ASSEMBLY THROUGH SAID TUBE MEANS, COUPLING MEANS BETWEEN SAID TUBE MEANS AND SAID RING DRILL BIT ARRANGED TO PERMIT RELATIVE ROTATION OF THE RING DRILL BIT WITH REGARD TO THE TUBE MEANS AND RETRACTION OF THE RING DRILL BIT BY THE TUBE MEANS, A MAIN ADAPTER ARRANGED TO FIT SAID CENTRAL DRILL BIT AND ROD ASSEMBLY AND TO TRANSMIT PERCUSSION AND ROTATIONAL ENERGY TO SAID ASSEMBLY, A FLUSHING WATER PASSAGE BETWEEN SAID ASSEMBLY AND SAID TUBE MEANS, A FLUSHING WATER SUPPLY BUSHING FITTED ON THE ASSEMBLY AND PROVIDED WITH PASSAGES FOR LEADING FLUSHING WATER TO SAID PASSAGE BETWEEN SAID ASSEMBLY AND SAID TUBE MEANS, A SHOULDER ON SAID MAIN ADAPTER ARRANGED FOR TRANSMITTING PERCUSSION ENERGY THROUGH SAID BUSHING TO SAID TUBE MEANS BUT PERMITTING ROTATIONAL MOVEMENT OF THE ADAPTER RELATIVE TO SAID TUBE MEANS, AND A CLAMP FOR HOLDING SAID TUBE MEANS AND SAID MAIN ADAPTER TOGETHER AXIALLY.
 7. IN ROCK DRILLING APPARATUS ADAPTED FOR DRILLING COAXIAL BORES OF TWO DIFFERENT DIAMETERS WITH BOTH AXIAL PERCUSSIVE MOTION AND ROTARY MOTION, THE COMBINATION WHICH COMPRISES A PERCUSSIVE RING DRILL BIT HAVING CUTTING EDGES DISPOSED THEREAROUND DEFINING THE DIAMETER OF THE LARGER OF SAID BORES AND AN OPEN CENTRAL PASSAGE AXIALLY DISPOSED THROUGH SAID RING DRILL BIT, A CENTRAL PERCUSSIVE DRILL BIT HAVING CUTTING EDGES DISPOSED THEREAROUND DEFINING THE DIAMETER OF THE SMALLER OF SAID BORES, THE DIAMETER OF SAID CENTRAL DRILL BIT BEING LESS THAN THE INTERNAL DIAMETER OF SAID AXIAL PASSAGE IN SAID RING DRILL BIT FOR FREE AXIAL MOVEMENT AND RETRACTION OF SAID CENTRAL DRILL BIT THROUGH SAID PASSAGE, A BIT ADAPTOR CONNECTED TO SAID CENTRAL DRILL BIT AND COAXIALLY DISPOSED WITH RESPECT THERETO IN SAID PASSAGE, MEANS ON SAID BIT ADAPTER FOR TRANSMITTING AXIAL DRILLING PERCUSSIONS TO SAID CENTRAL DRILL BIT, COOPERATING AND ENGAGING SUBSTANTIALLY TRANSVERSE SURFACES ON SAID BIT ADAPTOR AND SAID RING DRILL BIT FOR TRANSMITTING AXIAL DRILLING PERCUSSION TO SAID RING DRILL BIT ONLY IN A DRILLING DIRECTION, SAID BIT ADAPTOR BEING FREELY AXIALLY RETRACTABLE FROM SAID RING DRILL BIT IN THE OPPOSITE DIRECTION, AND ENGAGING MEANS ON SAID BIT ADAPTOR AND SAID RING DRILL BIT FOR TRANSMITTING ROTARY MOTION FROM SAID BIT ADAPTOR TO SAID RING DRILL BIT AND BEING FREELY AXIALLY DISENGAGEABLE UPON RETRACTION OF SAID BIT ADAPTOR FROM SAID RING DRILL BIT. 